Embedded dram memory cell with additional patterning layer for improved strap formation

Abstract

The present invention relates to semiconductor devices, and more particularly to a structure and method for forming memory cells in a semiconductor device using a patterning layer and etch sequence. The method includes forming trenches in a layered semiconductor structure, each trench having an inner sidewall adjacent a section of the layered semiconductor structure between the trenches and an outer sidewall opposite the inner sidewall. The trenches are filled with polysilicon and the patterning layer is formed over the layered semiconductor structure. An opening is then patterned through the patterning layer, the opening exposing the section of the layered semiconductor structure between the trenches and only a vertical portion of the polysilicon along the inner sidewall of each trench. The layered semiconductor structure is then etched. The patterning layer prevents a second vertical portion of the polysilicon along the outer sidewall of each trench from being removed. By adding the patterning layer over the semiconductor structure during trench type memory cell fabrication, strap resistance and its variation can be reduced, resulting in better DRAM cell operation with less process dependence and improved strap overlay formation.